1. Field of the Invention
The present invention relates to an orally-administrable therapeutic and/or prophylactic agent for HTLV-1 (Human T-cell Lymphotropic Virus Type 1) related diseases, and more particularly to an orally-administrable therapeutic and/or prophylactic agent for HTLV-1-related diseases, which comprises an interferon-.gamma. (abbreviated as IFN-.gamma. hereinafter) as an effective ingredient.
2. Description of the Prior Art
Adult T-cell leukemia (abbreviated as ATL hereinafter) is a T-cell leukemia with characteristic symptoms, found and reported by Cache TAKATSUKI in 1976. The disease is an intractable and district-specific disease, and in some cases it may cause a malignant lymphoma-like symptom; In Japan, there found many patients in the South and East Japan including Kyushu-, Okinawa- and Shikoku-Islands. In overseas, in the tropical regions such as the Caribbean Sea and the South India. Most of the leukemia cells induced by ATL have CD4-positive and CD8-negative helper T-cell surface antigens, and show a specific change in nuclear. It was revealed that ATL is induced by HTLV-1, a C-type retrovirus, as a causative virus thereof.
Epidemiological research revealed that HTLV-1-infected patients or HTLV-1 carriers may cause not only ATL but induce malignant tumors at a relatively-high efficiency, as well as neuropathies and immunopathies called HAM (HTLV-1-associated myelopathy). HTLV-1 is now being researched that, in addition to ATL, it correlates to another diseases. Furthermore, it is pointed out that HTLV-1 may relate to chronic rheumatoid arthritis, Sjogren syndrome, systemic lupus erythematosus (SLE), uveitis, etc.
HTLV-1 infection can be easily diagnosed by detecting an HTLV-specific antibody in blood and by confirming the presence of an HTLV-1 proviral DNA. Symptoms and developments of HTLV-1-infected patients are varied, and the patients may become to show the symptoms at their age of 50th. Physiologically, there observed the downfall of myelin sheathes and the loss of axons from the upper part of cervicals through lumbars, the invasion of mononuclear cells such as lymphocytes and macrophages, the proliferation of astrogrias, and a slight level of the mononuclear cells' invasion in the part of brain stem and the substantia alba of cerebrum and cerebellum.
The percentage of the incidence of ATL induced by HTLV-1 is relatively low. However, once occurred, the symptom of the patients infected with the virus is rapidly worsened, and the treatment is quite difficult. Conventional therapies include the administration of a relatively-large amount of adrenal cortical hormone, and chemical- and radio-therapies in accordance with those for malignant tumors. They are, however, merely temporal symptomatic therapies which are far from intrinsic therapy. As another clinical-test-treatment for ATL as an HTLV-1-related disease, Kazuyuki ISHIHARA proposed in Skin Cancer, Vol. 12, No. 2, pp. 301-314 (1997) an intramuscular injection of IFN-.gamma., where several millions units of IFN-.gamma. are injected to a patient daily for over eight weeks. In such a treatment, patients are forced to stay in hospitals or allowed to go to hospitals frequently, resulting in physical- and mental-pains and economical burdens. In the latter case, when patients unexpectedly could not go to hospitals on their prescribed administration dates, the medicinal administration control is not sufficiently conducted, and as a drawback, this hinders the expected therapeutic effect. Although IFN-.gamma. is per se a safer medicine which scarcely induces side effects even when administered to patients at a relatively-high dose, the above daily high-dose as much as several hundreds units of IFN-.gamma. may result in side effects such as serious depression of liver function, leukopenia, neutropenia, calcium lowering, and fervescence. In the most serious case, the administration must be ceased.
Under these backgrounds, greatly expected is the establishment of a relatively-safe medicine which can intrinsically and effectively treat and/or prevent HTLV-1-related diseases, and lower the patients' mental, physical, and economical burdens.